Fix AFS to write back dirty on unmounting.  This didn't happen because
afs_super_ops.drop_inode was pointing to generic_delete_inode.  Now this
pointer is left set to NULL so that the default behaviour occurs instead.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 static const struct super_operations afs_super_ops = {
        .statfs         = afs_statfs,
        .alloc_inode    = afs_alloc_inode,
-       .drop_inode     = generic_delete_inode,
        .write_inode    = afs_write_inode,
        .destroy_inode  = afs_destroy_inode,
        .clear_inode    = afs_clear_inode,